The present invention relates to a rotary magnetic head device for recording and playback device such as video tape recorder and the like.
The rotary magnetic head device comprises a fixed cylinder fixed on a shaft of motor, a rotary cylinder fixed on the shaft through a rotary disk, a magnetic head for recording and reproducing a video signal which is fixed on the rotary cylinder, and a transformer for transmitting signals which is disposed between both cylinders.
Mounting the magnetic head on the rotary cylinder may involve a problem that weight is unbalanced to the center of a rotation axis of the rotary cylinder due to misalignment by these assemblies, unevenness in density of material and the like. If weight becomes unbalanced, a centrifugal force is generated from turning the rotary cylinder, and thus vibration may result. The problem cannot be neglected particularly for the cylinder of miniature and light-weight construction. Now, therefore, a proper aperture is provided on the rotary cylinder and others hitherto, thereby lightening the unbalance in weight of the rotary cylinder.
However, as shown in FIG. 1, for example, in case two video heads 3 are disposed on a rotary cylinder 1 symmetrically with reference to the shaft center of the rotary cylinder 1, or at intervals of turning angle of 180.degree., and further one erase head 10 is mounted at a position 90.degree. in angle of rotation from the two video heads 3, an initial unbalance of the rotary cylinder 1 is heavy, and the aperture provided as above is still not to remove the initial unbalance. Accordingly, as shown in FIG. 1 and FIG. 2, an unbalance compensating weight 8 is mounted generally on the rotary cylinder 1, thereby minimizing the initial unbalance.
The weight 8 is fixed hitherto on the rotary cylinder 1 with a screw 9 or adhesive.
However, as shown in FIG. 3A and 3B, a dislocation of the weight 8 arises longitudinally or horizontally at the time of mounting, thus the initial unbalance cannot be removed thoroughly, and in addition the mounting work is not easy.